Pressure-Dependent Relaxation in the Photoexcited Mott InsulatorET–F2TCNQ: Influence of Hopping and Correlations on Quasiparticle Recombination Rates

M Mitrano,J Stähler,R Beyer,L Baldassarre,D Nicoletti,G Cotugno,D Jaksch,T Hasegawa,H Okamoto,A Perucchi,M Dressel,R Singla,S Kaiser,S R Clark,A Cavalleri

doi:10.1103/physrevlett.112.117801

Abstract

We measure the ultrafast recombination of photoexcited quasiparticles (holon-doublon pairs) in the one dimensional Mott insulator ET-F(2)TCNQ as a function of external pressure, which is used to tune the electronic structure. At each pressure value, we first fit the static optical properties and extract the electronic bandwidth t and the intersite correlation energy V. We then measure the recombination times as a function of pressure, and we correlate them with the corresponding microscopic parameters. We find that the recombination times scale differently than for metals and semiconductors. A fit to our data based on the time-dependent extended Hubbard Hamiltonian suggests that the competition between local recombination and delocalization of the Mott-Hubbard exciton dictates the efficiency of the recombination.

Highlights

We measure the ultrafast recombination of photoexcited quasiparticles in the one dimensional Mott insulator ET–F2TCNQ as a function of external pressure, which is used to tune the electronic structure
In the case of metals, the dynamics are well captured by the two-temperature model [1,2], which considers the energy stored in the optically excited nonequilibrium electron distribution as flowing into the lattice at a rate determined by the electronphonon coupling strength and by the electronic and lattice heat capacities
As the relaxation of hot electrons accelerates with smaller electronic specific heat, and because cev is proportional to the density of states at the Fermi level [3], for metals relaxation should accelerate linearly with the reciprocal of the bandwidth τ ∝ 1=t

Summary

Introduction

We measure the ultrafast recombination of photoexcited quasiparticles (holon-doublon pairs) in the one dimensional Mott insulator ET–F2TCNQ as a function of external pressure, which is used to tune the electronic structure. We first fit the static optical properties and extract the electronic bandwidth t and the intersite correlation energy V.

Results

Conclusion